The present invention relates to a homogenous additive composition containing a tall oil fatty acid, compatibilizer mixture and an aromatic solvent for use in a diesel fuel composition.
The sulfur content of diesel fuel is being lowered in a number of countries for environmental reasons. In the United States, ultra low sulfur diesel fuel will be mandated to have less than 15 ppm of sulfur by June of 2006. The process for preparing low sulfur content fuels in addition to reducing sulfur content also reduces the content of other components of the fuel such as polyaromatic components and polar components. It has been found, that reduction of these components has decreased the lubricity of the fuel. In some diesel engines, the fuel is the lubricant for the fuel system components, such as fuel pumps and injectors. Thus, the decreased lubricity of the ultra low sulfur diesel fuel has resulted in the fuel being less efficient in lubricating fuel system, especially the injection system.
This wear problem associated with low sulfur content diesel fuel can be reduced by providing a lubricity additive to the fuel composition. One such additive that has shown to provide wear reducing properties to low sulfur diesel fuel is tall oil fatty acid (see U.S. Pat. No. 2,907,646.) Most fuels are additized by injecting the additive into the fuel while it is being loaded into trucks at the terminal rack, or at the pipeline flange as the fuel is received at the terminal. The additive solution must be fluid, homogeneous and low viscosity this can be accomplished by formulating compositions to have low viscosity and compatibility at low temperature. Unfortunately, an additive such as tall oil fatty acid is not suitable as the sole component since it typically turns solid at 0° C. within one day.
EP 0789460A1 and U.S. Pat. No. 5,968,211 discloses an additive concentrate containing solubilizers to maintain the concentrate in the liquid state at low temperatures. Fatty acid, oligomers of such acids and the esters of such acids, useful as anti-friction and wear reducing additives in gasoline and diesel fuels are formulated into an additive concentrate which remains liquid at low temperatures of about −17° C. and lower by the additional presence in the concentrate of an alcohol, an amine, or a mixture of alcohol and amine. The fatty acids and their esters are typically derived from naturally occurring oils and include those known as tall oil acids and their esters.
EP0938533B1 and U.S. Pat. No. 6,277,158 discloses an additive concentrate for use in fuels, especially in gasoline for internal combustion engines. The invention provides an additive concentrate comprising by weight an ashless friction modifier which is liquid at room temperature and pressure selected from i) n-butylamine oleate or derivatives thereof, (ii) a substance comprising tall oil fatty acid or derivatives thereof, and (iii) a mixture of (i) and (ii) a deposit inhibitor, and a carrier fluid. Solubilizing agents for example hydrocarbon solvents such as alcohol may be included.
EP0829527A1 discloses an additive concentrate for use in fuels, especially in gasoline for internal combustion engines an ashless friction modifier which is liquid at room temperature and pressure selected from i) n-butylamine oleate or derivatives thereof, and (ii) a substance comprising tall oil fatty acid or derivatives thereof, and (iii) a mixture of (i) and (ii) a deposit inhibitor, and a carrier fluid.
WO 05/066317A1 discloses an invention to provide fuel lubricity compositions that improve lubricity over conventional additives. The invention provides a composition which contains corrosion inhibitors and/or stability additives along with lubricity additives are useful as fuel lubricity aids. The lubricity additives selected from ester-based additives and amide-based lubricity additives. The corrosion inhibitors selected from mono, dimer and trimer acids, succinic acids, imidazolines and stability additives selected from hindered primary, secondary and tertiary amines, amides, amine/aldehyde condensates and mixtures thereof.
The present invention, therefore, solves the problem of providing storage stability to the fuel, while maintaining lubricity by using an fuel additive package made up of specific grades of fatty acids higher in di-unsaturated fatty acids such as linoleic acid blended in an aromatic solvent and a compatibilizer mixture which consists of low molecular weight alcohols and low molecular weight acylated nitrogen compound, which is the reaction product of alkyl succinic anhydride and an alkanolamine. This fuel additive package containing the tall oil fatty acid, compatizer mixture and aromatic solvent can be kept homogeneous and have low viscosity at temperatures as low as −29° C.